An unrelenting chill prompted districts across Wisconsin to cancel classes Tuesday, a decision that means many schools will have to tack on additional days to the end of the school year.

At Antigo, Interim District Administrator Dr. Don Childs said today that, so far, local schoolchildren will see their school year extended from Wednesday, June 4 to Thursday, June 5. Teachers will hold their end-of-year workday on Friday, June 6.

Childs said some schools may also adjust classrooms minutes between now and the end of the term to make up for early release days.

“This is all assuming we don’t need any more snow days,” he said, adding more changes could be required depending on the weather, which remains notorious fickle into March.

Schools across the state had closed Monday as well, as a frigid blast of arctic air sent temperatures plunging near or below zero degrees. Schools also closed for one or two days earlier this month when a polar vortex swept across much of the U.S., bringing bone-chilling cold and dangerously low wind chills.

The Milwaukee County medical examiner’s office said Tuesday an 87-year-old Milwaukee woman may have died of the extreme cold. The woman was found in her backyard after apparently returning from a store. She had a body temperature of 37 degrees. An autopsy is scheduled for Wednesday.

Districts often build a few days into their calendars to account for days lost to inclement weather. But some have used up this year’s allotment and will need to add school days in June.

The students might not appreciate the extra days, but schools have little choice. Wisconsin districts are required to schedule 180 days of school, although up to five days can be used for parent-teacher conferences or snow days.

Classes in the Wausau School District were scheduled to end June 11, a date that included a two-day cushion in case school had to be called off for bad weather. Tuesday’s closure marked the third day this year that classes were canceled due to weather.

“We’ll be OK,” said Amy Arlen, a spokeswoman for the Wausau School District. “We are set for our summer classes to begin June 16. We could still have two more school days to make up if we needed to.”

When schools have to close for weather, the state Department of Public Instruction allows them to make up instruction time by adding class days or by extending the school day. The DPI leaves the decision up to the local communities, spokesman Patrick Gasper said in an email.

“The important matter to remember here is that everyone wants to ensure children are receiving the appropriate amount of instruction ... while ensuring the health, safety and well-being of their students and staff,” he said.

Other districts weighed options for meeting the minimum number of instruction days.

In the Marshfield School District, for example, leaders met with principals Tuesday morning to talk about how they would make up the time. The district essentially gets two snow days for free and then it has to make up additional time off. Monday and Tuesday were its third and fourth days off this school year.

Administrators decided to use two teacher in-service days to make up the time. If they have another snow/cold weather day, they have one more day — the day after Easter — that they could use.

“This is the first time in years that we’ve had to make up school days,” said Cathy Wingert, executive assistant to the superintendent.

Beyond that, they would likely add time to each school day, perhaps 5 to 15 minutes per day, she said. But the logistics could be challenging, she added.

“We’ve never had to go that far, so I don’t know how we’d do it,” she said.